There is known in the art comminuting machines or apparatus utilizing an impact hammer for comminuting, crushing, pulverizing, shearing, or cutting various materials such as wood products, waste wood, ores, concrete, aggregate, soft metal, scrap, and the like. For this purpose, there are two types of comminuters; namely, the fixed or stationary comminuter, and the swinging hammer comminuter, and machines of both types have been in use for many years and are used extensively in commercial operations.
In general, a fixed comminuter comprises a housing with a reducing chamber having an inlet for feeding material to the reducing chamber and an outlet for discharging material of reduced size. An impact rotor is arranged in the reducing chamber, and is mounted on a horizontal drive shaft driven by a suitable motor. A plurality of hammers or strikers are mounted along the periphery of the rotor or radially of the rotor, and each hammer has a striking or impact surface oriented in the general direction of rotation of the rotor. The feed is directed against the striking or impact surface of the hammer and repelled with force against an anvil spaced from the hammers. The impact of the material against the hammers and anvil, and any ricocheting of the material in the chamber, reduces the size of the feed. That is, during each revolution of the rotor, the feed pieces are sheared, cut, ground, etc., during each revolution of the rotor.
A swinging hammer comminuter generally includes a hammer pivotally connected to a rotor, and the hammer is free to swing as the rotor revolves. The hammer has an impact or striking surface oriented in the direction of rotation of the rotor, and feed material is directed against the impact surface, thereby resulting in size reduction of the feed as explained above with reference to the stationary comminuter.
Although machines or apparatus of this type have been in common use for many years, a distinct disadvantage with the machine is that the hammer or striker is subject to wear and deterioration. The leading edge, sometimes referred to as the cutting edge or outboard edge, of the hammer performs most of the cutting action of the feed material, and therefore encounters most of the impact forces. As a consequence, the hammer must be replaced with frequency depending on such factors as the type of feed and the inertia of the rotor. Also, the hammer is fastened to the rotor with relatively large bolts capable of exhibiting a torque of about 1,600 foot pounds per inch or higher. As a result of the high impact forces created by the inertia of the rotor, the bolts become fatigued or distorted, and as a consequence fail, which can occur before the cutting edge of the impact hammer deteriorates. Hence, downtime of a machine is relatively frequent because of failure of the fastening bolts, or deterioration of the hammer, or both. In a typical comminuter for cutting wood product, sometimes referred to in the art as a wood hog, nine to twenty four hammers are arranged on a rotor. When a replacement of worn parts is required, to change, for example, nine hammers takes about nine man hours, which translates into downtime or idling of a machine and additional man hours lost by idling loaders and unloaders.
This invention has therefore as it purpose to provide an improved impact member requiring substantially less downtime to change as compared to the conventional hammer, and is very cost effective.